CMT Joining of AA6061-T6 and AA6082-T6 and Examining Mechanical Properties and Microstructural Characterization

Abstract

Nowadays, CMT is used for joining dissimilar thickness of dissimilar metals for achieving higher mechanical strength by using properties of both the metals. Joining of dissimilar aluminium alloys with dissimilar thickness by using gas metal arc welding with cold metal transfer (GMAW-CMT) process, is the primary objective of this work. CMT butt joining of 6061-T6 (3.18 mm) and 6082-T6 (2 mm) aluminium alloys was carried out by using ER4043 (Al-5%Si) wire. Mechanical properties and microstructural characterization were carried out for the weld bead. Microstructural examination at different weld zones is studied using optical microscope and field emission scanning electron microscope (FESEM). Macrostructural images were captured to study the weld bead geometry in relation to heat input. Mechanical properties were examined by Vicker's microhardness and tensile test (with reinforcement, that is, the actual profile of the bead and without reinforcement, that is, the profile of bead are flattened to the surface of the plate). The residual stresses were measured using high-resolution X-ray diffraction (HR-XRD) method. Results showed significant changes in mechanical properties when heat input was in the range of 120-130 J/mm. Removal of reinforcement height improved almost 7-11% of tensile strength. Compressive residual stresses were experienced in the weldment. Comparatively cold metal transfer (CMT) showed better residual stress results than metal inert gas (MIG) welding at the same heat input.